Anyone who is sexually active risks exposure to a sexually transmitted infection to some degree. Factors that may increase that risk include:

  • Having unprotected sex. Vaginal or anal penetration by an infected partner who is not wearing a latex condom transmits some diseases with particular efficiency. Without a condom, a man who has gonorrhea has a 70 to 80 percent chance of infecting his female partner in a single act of vaginal intercourse. Improper or inconsistent use of condoms can also increase your risk. Oral sex is less risky but may still transmit infection without a latex condom or dental dam. Dental dams — thin, square pieces of rubber made with latex or silicone — prevent skin-to-skin contact.
  • Having sexual contact with multiple partners. The more people you have sexual contact with, the greater your overall exposure risks. This is true for concurrent partners as well as monogamous consecutive relationships.
  • Having a history of STIs. Being infected with one STI makes it much easier for another STI to take hold. If you're infected with herpes, syphilis, gonorrhea or chlamydia and you have unprotected sex with an HIV-positive partner, you're more likely to contract HIV. Also, it's possible to be reinfected by the same infected partner if he or she isn't also treated.
  • Abusing alcohol or using recreational drugs. Substance abuse can inhibit your judgment, making you more willing to participate in risky behaviors.
  • Injecting drugs. Needle sharing spreads many serious infections, including HIV, hepatitis B and hepatitis C. If you acquire HIV by injecting drugs, you can transmit it sexually.
  • Being an adolescent female. In adolescent girls, the immature cervix is made up of constantly changing cells. These unstable cells make the adolescent female cervix more vulnerable to certain sexually transmitted organisms.

According to a surveillance report from the Centers for Disease Control and Prevention, sexually transmitted infections are more common among certain groups, such as young people, men who have sex with men, and minority communities. The theory is that potential sex partners often belong to social networks made up of people of similar age, location and background. Within these overlapping networks, couples regularly form, split up and find new partners. If one STI is making its way through such a network, there's a good chance that others are, too.

Transmission from mother to infant

Certain STIs such as gonorrhea, chlamydia, HIV and syphilis can be passed from an infected mother to her child during pregnancy or delivery. STIs in infants can cause serious problems and may be fatal. All pregnant women should be screened for these infections and treated.

Feb. 23, 2013